Analysis Of The Effects Of Vibration Modes On Fatigue Damage In 25t Passenger Carbody

The lightweight design of the railway vehicle structure can effectively reduce the force under the wheel-rail dynamic conditions,reduce the vehicle manufacturing cost and cost,and thereby improve the safety of vehicle operation and the reliability of operation.The carbody structure is the main support part of the railway locomotive power vehicle.It has the characteristics of complex structure,large weight,welded forming overall load,and multi-axle complex fatigue load.Lightweight design of the carbody has the effect of reducing the weight of the entire vehicle.Significant effect.The lightweight design of the carbody reduces its own modal frequency,which causes the modal frequency of the carbody to be closer to the frequency range of external load excitation,which stimulates the carbody to intensify vibration and cause fatigue failure.Studying the influence of modal on the fatigue damage of the carbody is beneficial to avoid harmful modalities in design and provide a basis for the dynamic design of the carbody.Therefore,this paper systematically carries out the modal analysis of the lightweight carbody,the calculation of the multi-axis load spectrum of the carbody and the use of the modal superposition method to analyze the influence of the modal on the fatigue damage of the carbody,and the lightweight and dynamic of the carbody.The design has important engineering and practical value.Firstly,a multi-car multi-body system dynamics model of 25 T passenger car was established,and nonlinear factors in the system model were taken into account,and American5-level spectrum track excitation was applied.The 25 T passenger car was calculated on the selected line-Beijing-Qingdao line.The load time history corresponding to each working condition is superimposed on the load time history of the coupler under the actual working condition based on the train traction and braking characteristic curve.Based on this,the multiaxle load spectrum of each force part of the carbody under typical operating conditions is compiled.On this basis,Fourier transform(FFT)and power spectral density conversion are performed on the obtained load spectrum,and the corresponding frequency domain load spectrum and power spectral density function(PSD)are obtained,and the time domain and frequency domain characteristics of the load spectrum are obtained.了 Analysis.Then,a finite element model based on the car body was established,and its mechanical stiffness and modal were calculated,and the correlation with the actual test results was comprehensively analyzed to illustrate the validity of the calculated results.The relationship between the stiffness and modal frequency of the carbody parameterized optimization model is analyzed,and the relationship curve between stiffness and modal frequency is obtained by fitting,which proves that the equivalent bending stiffness of the carbody is linear with the carbody’s vertical bending modal frequency.Relationship,the equivalent torsional stiffness is linear with the torsional mode of the carbody.A finite element model was established for the lightweight and optimized carbody,and its stiffness and modal were analyzed.Finally,the quasi-static superposition method and the modal superposition method are used to calculate the fatigue damage of the carbody.The quasi-static superposition method combines the static strength analysis under unit load with the material SN curve and random load spectrum,and based on the Miner linear cumulative damage theory,the fatigue damage and life of the carbody before and after the optimization are calculated.The quasi-static superposition method is used in the calculation of the carbody The damage provides a reference for the comparison of carbody fatigue damage under the influence of modal.The modal superposition method is used to calculate the modalities of the prepared carbody before and after the optimization,and the random load spectrum is applied to the carbody to obtain the modal displacement response of the carbody.The superposition of each main mode and the first 30 modes are calculated separately After the modal stress,combined with the material SN curve and the Miner cumulative damage theory,the influence of the modal on the fatigue damage of the carbody is analyzed.Using the analysis method in this paper,we found the modals with greater fatigue damage to the carbody before and after the lightweight design.The load excitation on the carbody contains frequency components that cause greater damage to the corresponding modal.Therefore,in order to improve the vibration fatigue reliability of the carbody structure,attention should be paid from two aspects of track excitation and the carbody’s own modal.